Washer stand pipe requirements

I know the trap should be 6-8 inches from the floor and the stand pipe should be between 18 and 30 inches. I'm helping my sister remodel her laundry room and the drain appears to be installed incorrectly. The trap is too high and the stand pipe is too short all with 1 1/2" abs. It was working fine with her old washer but now she is installing a HE frontloader. The wall is cinderbloack,on a concrete slab, and the drain coming out of the wall is approx 24 up from the floor. Can I turn 90 down and put the trap in the correct location and also lengthen the stand pipe at the same time or do I need to lower the drain in the wall?

Is it broke? If not, don't fix it! If you get back-up from a washer that discharges too much at once, then do everything possible to get the drain up to
code-minumum (most places) size of 2 inches. Or install a basin to catch the washer drainage.

NO, you cannot loop around down to get things at the desired height - you'd have to drop the connection in the wall first. You CAN extend the standpipe (the pump should easily pump it higher), but being 1.5", it may not be enough. If the pipe in the wall is 2", then you should redo it in 2". If it isn't, not sure just raising the standpipe would do much. You could just use a nohub connector and a piece of pipe to check it out easily and cheaply, though.

With top loading washers, there's no such thing as a "supposed ta be" height for the top of the stand pipe. As long as the top of the stand pipe is above the elevation of the water in the machine during the wash cycle, then that's all that's needed. That's cuz if the drain hose for the washer were below the level of water in the machine, water would be spilling out of that hose during the wash and rinse cycles. It's the fact that the drain hose is above the water level in the machine that keeps the wash water inside the washer.

So, I'd follow the same rule for your front loader. Hold the end of the drain hose at the elevation it'd be if it was inserted into your stand pipe, and see if any water comes out during a wash cycle. If it's nada, then the existing height of your stand pipe will keep all the water in your washer during a wash cycle and you don't need your stand pipe to be any higher than it already is.

Now, your washing machine is the canary in the coal mine when it comes to assessing the condition of your house's drain piping. That's cuz the washing machine pumps more water into your house's drain piping faster than any other appliance or fixture. So, if it turns out that your stand pipe backs up when you do laundry, it's very possible that the main drain line from your house is partially clogged up (mostly with solids from your kitchen sink), and the washer is pumping water into your drain piping faster than that water can flow through any partially clogged section of drain piping. So, if you have any water backing up as a result of doing laundry, I'd have your main drain line snaked out to remove any partial clogs.

But, if it turns out that even after cleaning the drain pipes you still get water backing up on you and you're convinced that your drain is too small, then besides redoing the drain piping with 2 inch ABS, I'd consider splicing a gate valve into the washer's drain hose and leaving partially closed to restrict the rate at which water gets pumped out of your washer. The pumps in washing machine have rubber impellers which won't be harmed by pins, buttons, coins and other stuff going through the pump. Your pump won't be harmed by restricting the flow out of the washer. All that'll happen is that it'll take a few seconds longer to pump the water out of the washing machine, but they won't feel any wetter at the end of the final spin cycle.

I do not think I have ever installed a washer "P" trap 6" to 8" above the floor. 12" or higher, even 24" if necessary, would be my normal location. With a 1 1/2" drain ANYTHING you do to it, including your suggestions, will make it drain worse. If it does not drain properly, the way it is, then the only solution is to open the wall and install a 2" P trap and drain riser.

i think the real key phrase is PROPERLY INSTALLED....if installed properly the drain shouldn't clog as there's lots of flow for self cleansing...either way, my intent was not to start an argument, it's just an interesting difference between our codes. I would think there would be a reason you all seem to use 2", but would think that the same possible problems would be apparent across the board.

The US codes tend to be written and ammended to account for those 'what-if' situations, like what happens when someone stands on the drain in a shower, or you decide to install a car wash there - a 2" drain has nearly double the capacity of a 1.5" one. With the newer front-loading WM that can approach 2000rpm, it can move a lot of water fast. Older ones just don't move it as fast. So, for a margin of error, the US calls for a 2" pipe.

Actually, a two-incher has EIGHT times the drainage capacity of an 1 1/2 drain, at least as measured by allowable Drainage Fixture Unit loading.

Click to expand...

Yes, but from a simple total area of the opening, it's just under twice as big...bigger pipes flow waste with less restrictions, and have a disproportionate increase in capacity (i.e., it is not linear).